Diesel fuel ignition accelerator



DEIESEIL EGNJITKQN ALCEELEMTOR No Brawn-ls.

Application May 4, 1939,

Serial No. Wit-233 i Ciai.

This invention relates to an improvement of hydrocarbon fuels byaddition compounds serving to accelerate their ignition incompressionignition engines chiefly of the high speed type,

5 commonly known as Diesel engines.

The beneficial action of addition compounds which shorten the delayperiod between injection of a fuel and its ignition efiectedspontaneously with compressed air in 2. Diesel engine is 30 well known.A number of addition compounds have been proposed for this generalpurpose. Among the most efiective compounds heretofore recommended tofunction as ignition accelerators of hydrocarbon Diesel fuels areorganic nitric i5 and nitrous esters. To oil'set acid forming tendenciesof such esters other compounds of more basic character have also beenproposed, for example, some oximes and amines which, in genoral, arerelatively less effective for inducing 2c ignition oi. the fuel.

An object of the present invention is to im prove Diesel fuels bynormally stable oil-soluble addition compounds having base formingtendencies but with high efiectiveness for acceleratlog ignition morecomparable to that of alkyl nitrates. As a further object, thisinvention provides a method of modifying oxy-nitrogen groupscharacteristic of nitro, nitroso, and oximino compounds to obtain theimproved Diesel fuel ignition accelerators.

It has now been found that alkylating or acylating aliphatic oximes andrelated compounds, particularly at the functional group, a markedimprovement is made in their ignition accelerating action as well as intheir oil solubility and stability in storage.

Aliphatic oximes are compounds containing the group Other compoundssimilar in structure and behavior are isomeric forms of aliphatic nitroand nitroso compounds known as iso-nitroso and isonitro compounds. Theoximes are generally re garded as derivatives of aldehydes and ketones,

according to whether their structure is RCHzNOH or \C:NOH

These structures are the same for the tautomeric and isomerictransformation products of pri- (Ci. a l-9) mary and secondary nitrosocompounds, which contain groups -CI-I2-NO and Similarly, primary andsecondary nitroparaflins are considered to assume the tautomeric andisomeric forms having the structures It is well known that the majorityof the de-- scribed aliphatic oximino compounds are solid at roomtemperature, have low hydrocarbon oil solubflity, and are in someinstances water soluble.

By the action of alkylating agents, oximes are converted into etheroximes which dissolve in hydrocarbon oils with ease. The etherifying ofthe oximes, or alkylation of the oximino group, is readily attained bythe use of reagents, such as dimethyl sulfate in the presence of causticsoda, alkyl iodides, or other known alkylating agents. An etherextraction may be made of the alkylation product to recover the desiredfinal product having the type formula NOR" and

NOR"

in which R, R, and R", represent aliphatic groups, e. g., a methylgroup, or homologous r ups.

The term aliphatic radical, as used herein and in the claims, refers toopen chain groups containing hydrogen and carbon, e. g., alkylene,a1ky1,or acyl. 45

0f equivalent value are the ethers or esters in which R or R" is an acylgroup, as in NOOCHI or as in l|-|IOCHa R-C-OCH: These may be obtained,for example, by etherify- 55 2 a,22s,1e1

ing acetyl aldoxime and by acylation of iso-nitro compounds. A generalmethod for preparing the methyl ester oximes (R-CHzNO-OClh) involves thereaction of diazo methane with primary 1 a nitro-paramns behaving in thereaction as isonitro compounds.

It has been found that the esterifled and etherified oximes aresubstances more soluble than the unmodified oximes in hydrocarbon oils.

10 Also, they have been observed to act more generally in a basic orneutral manner and are thus able to minimize the development of aciditymore effectively.

There are a number of well known-ways for 1 l5 obtaining compounds to beconverted into ether or esteroximes. Some of the principal methods areoutlined below:

1. Aliphatic nitroso or nitro compounds which have strong tendencies torearrange into oximes 20 are obtained readily by reacting nitrousanhydride, nitric anhydride, or nltrosyl chloride with olefins,particularly branched oleflns.

2. Ketones react with nitrous esters or with nitrous acid to form oximes(iso-nitrosm 25 ketones) 3. Aldehydes and ketones react with hydroxylamine to yield aidoximes and ketoximes.

Oximcs can be formed from 1:2 and 1:4 diketones also from varioushydroxy aldehydes' and 130 ketones, e. g., glycol aldehyde, aldol,acetyl carbinol, acetoin, etc.

Starting with an oximino compound or compound capable of reacting asoximino compound regardless of its origin, the etheriiication of the 35ommino group (=NOH) is effected by the general reaction:

wherethe R groups represent aliphatic radicals and RnH represents anallrylating agent, e. g.. dirnethyl sulfate, methyl iodide, isopropyliodide, etc. Preferably a basic catalyst, e. g., potassium carbonate,caustic soda, sodium ethylate, silver oxide, or the like, is employed.

Example 1 tilled under reduced pressure at about 50 C. (25

to 32 mm. mercury absolute) giving a yield of about 40 to 50%theoretical.

- so Example 2 Preparation of the methyl ether of iso-nitroso methylacetone (methyl ether or nitrone of diacetyl monoxime).

5 om-co-ccn-ocmi on:

One mole of iso-nitroso methyl acetone (iso- 1 nitroso methyl ethylketone) in an excess of NaOH and shaken for about to A hours withdim'ethyl sulfate at about 45 C. An. oily liquid 70 resulting as thedimethyl sulfate disappears, is extracted with ether and dried.

Comparisons of ignition accelerating action 3 demonstrate definitelythat the ester and ether crimes have more than twice the potency of the75 best oximes or nitroparaiiins.

ether and finally dried with K2003 may be dis- Tests were made on anumber of samples prepared by dissolving from less than 1% to about 3%by volume of each compound to be evaluated in a portion of a 40 octanenumber gas oil, the tests being made with a high speed C. F. R. Diesel 5engine according to the method disclosed in the S. A. E. Journal ofJune, 1936, page 225. Each sample was given a cetane number rating whichwas determined by the percentage of normal cetane in a blend consistingof normal octane l0 and alpha-methyl naphthalene giving comparableperformance in the test engine. Since the ignition lag of a blendconsisting of normal cetane I and alphamethyl naphthalene is shortenedvery nearly in proportion to the increase in percentage of cetane byvolume, the ignition quality improvement of a hydrocarbon fuel by anaddition compound can be determined in terms of the cetane numberincrease imparted to the fuel by the addition compound.

Among the oxlmes tested were acetone oxime, butyraldoxime,N-heptaldoxime, cyclohexanon oxime, iso-nitroso acetophenone, and acetylmonomethoxime. Most of these oximino compounds v{oi-m saturatedsolutions with the Diesel fuel in concentrations of less than 1%. Thisis particularly true of the cyclic oximes and acetyl monomethoxime. Inno instance, did the oximes confer upon the fuel an increase in cetanenumber greater than about +1 or +2. In almost all instances the cetanerating change was null or negative. In contrast thereto, theircorresponding esters and ethers are more soluble in hydrocarbon fuels,to the extent of 3% and higher, and for concentrations of about 1%increase the octane number of the fuel by at least, +4 and more, makingthese compounds of practical sin:- nificance.

It will be appreciated that the present invention is not restricted toany particular type of 0 alkylated oxime because any compound containingan oximino group (:N-OH) is subject to the same type of alteration byetherification or e-steriflcation.

Every type of oil suitable as a fuel for Diesel 5 engines may beimproved by the alkylated oximes added thereto in amounts from afraction of 1% to the limit of the solubility, preferably from about .5%to 5%. In most general use a hydrocarbon oil boiling above the boilingrange of gasoline or kerosene, such as the gas oil fraction used in thetests, would constitute the major proportion of the fuel because acompression-ignition engine operates more satisfactorily with liquidfuel injection. For proper functioning of liquid fuel injection systems,the fuel should have a viscmity of about 30 to Saybolt seconds at 110 F.Ordinarily a petroleum distillate boiling in the range of 375 to 700 F.has the desired physical characteristics of a Diesel fuel. m

The specific advantages of this invention over the prior art result fromthe decreased vapor pressure, greater oil solubility, stability,ignition accelerating potency, and reduced acidity imparted to oximocompounds by etheriflcation or 65 esteriflcation of the oxlminofunction.

Small quantities of these improved addition agents may be used forimproving crude high boiling distillate or residual oils of any basestock, whether it be parafllnic or naphthenic, and with bituminousdestructive distillation products or extracts. They may be used withother addition agents for improving other qualities of the oil ortogether with other ignition quality promoters,

e. g., nitrates. It is evident that the modified oximino compound mayalso contain other functional groups which make organic compounds moresensitive to ignition, for example nitrate groups or known sulfurgroups. Also sulfur anumalogues of the ether or ester oximes may be Theforegoing description and examples are to be taken as illustrative onlyand not as limiting the scope of the invention. Any modification orvariation therefrom conforming to the spirit of the invention isintended to be included within the scope of the claims. a

We claim:

1. A composition of matter comprising a hydrocarbon oil having a higherboiling range and viscosity than kerosene blended with a. minorproportion of a compound having the type formula:

vonl! Int-B where R, R and R" are aliphatic radicals.

-2. A compression-ignition engine fuel comprising a hydrocarbon Dieselfuel blended with a minor quantity of an ether oxime in sufllcientamount to improve the ignition quality of the fuel.

3. A compression-ignition engine fuel comprising a hydrocarbon Dieselfuel blended with a. minor quantity of an alkyl ether derivative of anoximino compound.

4. A compression-ignition engine fuel comprising a hydrocarbon Dieselfuel and a minor quantity of allwl ether of an iso-nitroso ketone.

5. A compression-ignition; engine fuel comprising a hydrocarbon Dieselfuel blended with methyl ether of iso-nitroso methyl acetone.

6. A compression-ignition engine fuel comprising a hydrocarbon Dieselfuel blended with an alkyl ether of a ketoxime.

'7. A compression-ignition engine fuel comprising a hydrocarbon Dieselfuel blended with an allwl ether of an aldoxime.

PHARIS MILLER. GOULD H. CLOUD.

